Electrochemical sensors are useful in chemistry and medicine to determine the presence or concentration of a biological analyte. Such sensors are useful, for example, to monitor glucose in diabetic patients and lactate during critical care events. A variety of intravascular, transcutaneous and implantable sensors have been developed for continuously detecting and quantifying blood analytes, such as blood glucose levels.
However, performance of enzymatic glucose sensors is affected by the amount of oxygen present at the electrode surface. For example, in enzymatic glucose sensors which rely on oxygen as an electron mediator, sensor signal decreases under low oxygen conditions (such as at about 0.25 mg/L or lower) for the same glucose concentration. Unfortunately, these performance issues are amplified in sensors with increased glucose sensitivity. As enzymatic glucose sensors capable of increased glucose sensitivity are developed, there is a desire for improved sensor performance under low oxygen conditions.
Additionally, the enzymes used in enzymatic glucose sensors are sensitive to temperature and pH degradation. Thus, the processes for manufacturing enzymatic glucose sensors are required to be conducted under pH and temperature conditions which preserve enzymatic activity. For example, polymer membrane curing that occurs after application of an enzyme layer is limited to temperatures at which the enzyme does not degrade, which are typically well below preferred curing temperatures for the polymer. Curing polymer membranes at these restricted temperatures extends curing time, increasing cost and limiting throughput. Accordingly, there is a desire for enzyme stabilization in enzymatic glucose sensors so as to provide enhancement in the tolerable pH range and increased thermal stability in order to decrease manufacturing time and cost.